The present invention relates to a method for producing a material for diffusion transfer process and in particular to a method for producing a photosensitive material for silver complex diffusion transfer process.
In silver complex diffusion transfer process, in general a photosensitive material comprising a support and, provided thereon, a silver halide emulsion layer as a photosensitive layer, an image receiving material comprising a support and an image receiving layer containing physical development nuclei coated thereon and a processing solution containing a solvent for silver halide.
That is, the theory of silver complex diffusion transfer process (hereinafter referred to as "DTR process") is as follows: Silver halide of exposed portion of exposed photosensitive layer is developed with a developing agent in the processing solution or the photosensitive material and simultaneously silver halide of unexposed portion reacts with silver halide solvent to become a soluble silver complex salt, which diffuses into the image receiving material and is deposited at physical development nuclei in the image receiving layer to form a silver image.
The DTR process based on such theory has been widely used for copying of documents such as printed matters, hand written matters, and design drawings and for production of block copies in plate making. Merit of DTR process is that super-high contrast and reproducibility of dots comparable to those obtained by commercially available lith film can be obtained by bringing into close contact a photosensitive material for DTR and an image receiving material in a DTR processing solution using a simple processor and besides maintenance of processing solution is easier than in lith system.
Hitherto, processing solution generally contains a developing agent, but recently for improvement of endurance of processing solution, the developing agent is contained in DTR materials and an alkali activation solution containing no or substantially no developing agent is used.
The present invention also relates to DTR materials which can be processed with such alkali activation solution.
DTR process is superior in that processing is simple as mentioned above, but is unsatisfactory in temperature control of processing solution and is liable to result in change of sensitivity and density. Further, one important property required for photosensitive material used for DTR process is to afford high transfer density in image receiving material. There is a method to increase amount of silver to be coated on photosensitive material for obtaining high transfer density, but this method is not preferred from the points of cost and saving of silver resources.
Hydrophilic binders advantageous for making photosensitive materials include proteins such as lime treated gelatin, acid treated gelatin, gelatin derivatives (such as those disclosed in Japanese Patent Kokoku Nos. 38-854, 39-5514, 40-12237 and 42-26345, U.S. Pat. Nos. 2,525,753, 2,594,293, 2,614,928, 2,763,639, 3,118,766, 3,132,945, 3,186,846, and 3,312,553, and British Patent Nos. 861,414 and 1,033,186), albumin, and casein, cellulose compounds such as carboxymethyl-cellulose and hydroxymethylcellulose, natural polymers such as agar and sodium alginate, and synthetic hydrophilic binders such as polyvinyl alcohol, poly-N-vinylpyrrolidone, polyacrylic acid copolymer, polyacrylamide and partial hydrolyzates of these derivatives. These hydrophilic binders may be used singly or in combination.
In general, photosensitive materials with hydrophilic binder at least a part of which is gelatin are used and normally these photosensitive materials are dried at low temperature in order to form a uniform surface of coat like ordinary photographic photo-sensitive layer, utilizing sol-formation and gelation phenomena of gelatin. As mentioned in Yuji Harazaki, "Coating Engineering", pages 278-281 (1971) published from Asakura Shoten, the drying process is divided into three of a period of preheating of the material, a period of constant-rate drying where evaporation amount of solvent per unit time, namely, evaporation rate of solvent is constant, and a subsequent period of falling-rate drying where evaporation rate of solvent gradually decreases and finally substantially no evaporation occurs (namely, the coat becomes to have substantially equilibrium water content under outer temperature and relative humidity conditions). If necessary, a humidity controlling period may further be provided. Usually, when equilibrium water content has reached about 5-8% by weight, drying is completed, but if temperature of surface of coat during drying (which is referred to as "surface wet-bulb temperature" in this specification) is lowered, uniform coat is obtained. However, according to the above drying method, it was impossible in case of photosensitive material for silver complex diffusion transfer process containing a hydroxybenzene derivative developing agent to obtain high transfer density and to inhibit deflection of sensitivity and density due to variation of temperature during processing.